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Water Hyacinth

Water hyacinth1

Water hyacinth2

Water hyacinth3

Pontederia

Villarsia reniformis

family

Pontederiaceae

Status

Water hyacinth (Eichhornia crassipes) is listed as a Weed of National Significance. In NSW it is a class 2 (notifiable) noxious weed in all Local Control Areas of the Southern Tablelands and South East Region except for Illawarra and Shoalhaven LCAs, where it is listed in class 3. It cannot be sold or propagated or knowingly distributed.

Description

Water hyacinth is unattached and floats on the water surface, forming dense mats. It is quite a substantial plant, varying from 10cm to 1m in height depending on nutrient levels. Leaves are glossy, fleshy and spoon-shaped, with a swollen flotation chamber at the base of the leaf stalk. Flowers are in spikes, large and mauve.

preferred habitat and impacts

Fresh water bodies such as farm dams, lagoons on river floodplains, rivers and creeks. Still or slow flowing water is usually preferred, but it can spread downstream on flowing water.Hyacinth blankets the water surface reducing light levels, temperature and oxygen in the water below. This has profound effects on communities of native plants and animals in the water. It also interferes with animal access for drinking water, human access for swimming and boating, reduces water quality and blocks pumps.

dispersal

Dumping of aquarium or ornamental pond plants is often the means of spread for aquatic weeds. Many will spread from broken-off pieces or whole plants being moved on boats or fishing equipment from an infested to a clean water body, or can be washed out of lagoons into river systems during floods.

look-alikes

The broad fleshy leaves, floating habit and showy mauve flowers of water hyacinth are unmistakable. A related exotic plant is blue pickerel weed (Pontederia cordata), which is often planted as an ornamental around garden water features. It is a taller plant which is rooted in soil at the water’s edge. It also has glossy spoon-shaped leaves and tall crowded spikes of smaller mauve or rarely white flowers. The native plant Villarsia reniformis has glossy, fleshy kidney-shaped leaves, the back of which are dotted with dark pores. They do not have the swollen bases of water hyacinth leaves. It is usually found in shallow or temporary pools where it is rooted in mud round the water's edge, sending out long runners. Its flowers are yellow with 5 petals.

Anchored water hyacinth (Eichhornia azurea) is very similar to water hyacinth, but as the name suggests, it is anchored in mud, not free-floating. It is not known to occur in Australia yet, but could be inadvertently introduced as an aquarium plant. It is listed a a class 1 noxious weed throughout NSW. View the fact sheet for this species below.

control

Most importantly, do not dump unwanted aquatic plants into water bodies, or grow species with weed potential in ornamental ponds or aquaria. Some invasive water plants are still sometimes sold by nurseries or pet shops. If you notice this, report the instance to Council, so that the proprietors can be advised that it is illegal to sell these plants.Once an infestation is established, and has been definitely identified, there are two options, mechanical or chemical control. Floating plants such as water hyacinth can be raked to shore or pulled in with an encircling rope, and piled on the shore above flood reach under plastic, where they will break down rapidly. For large infestations, herbicide may be required, but a permit will be required from the Environmental Protection Agency to apply any herbicide to a water body. Only a limited number of herbicides are registered for use over water. Notify your local weed control authority (usually Council) and take their advice on control methods.